The present invention relates to the art of computer driven inkjet printing devices, like ink jet printers, multi-function printing/scanning devices, faxes, copiers or the like. Devices of this type have a printhead carriage which is mounted for reciprocal movement on the device in a direction orthogonal to the direction of movement of the paper or other medium on which printing is to take place through the device. For sake of simplicity, in the following we refer to an inkjet printer only, but the same will apply to any inkjet printing devices, mutatis mutandis. The printer carriage of a printer typically has from one to four or more ink jet printheads mounted thereon, e.g. piezoelectric or thermal printhead. Each of the printheads contains a supply of ink which, for large scale printers, is generally inadequate due to the large volumes of ink which are required as compared with the ink supply requirements of desk top printers. Consequently, various means have been proposed for continuously or periodically refilling the carriage-borne printheads with ink. These systems fall into two categories. The first comprises off-board or off-axis ink reservoirs which are continuously connected to the carriage-borne or onboard printheads by flexible tubes. The second comprises a xe2x80x9ctake a gulpxe2x80x9d system in which the printhead carriage is periodically moved to one end of its path of travel where it is then connected with off-axis ink reservoirs to fill the onboard printheads. This xe2x80x9ctake a gulpxe2x80x9d system is disclosed in Hewlett-Packard""s Designjet 2000 printer referred to in U.S. patent application Ser. No. 08/805,861 filed Mar. 3, 1997 and published in European Patent Publication No. 0863016 on Sep. 9, 1998.
Large format printers are expensive pieces of equipment which preferably should be capable of using different types of ink without significant modification of the printer. The different ink types may for convenience be broadly referred to as indoor ink and outdoor ink, meaning ink intended to be used for production of drawings, posters, and other printed material which may be displayed outdoors or indoors. Outdoor ink is pigment based, i.e. containing a plurality of discrete undissolved pigment particles suspended in a fluid carrier. Dye-based ink has a lower degree of optical density and permanence but is less expensive.
Further, in color printers four separate colors of ink are usually employed comprising black and three primary or mid-primary colors such as cyan, magenta and yellow. In color ink printers provision must also be made to ensure that neither incorrect types of ink nor incorrect colors of ink can inadvertently be used in the system.
Since the ink delivery tubes connected from off-board reservoirs to onboard printheads continually flex, leakage and breakage of the ink supply tubes is experienced. A reliable ink delivery system and guides for routing the ink delivery tubes to minimize flexing and breakage is desired.
U.S. patent application Ser. No. 09/240,091 filed on Jan. 29, 1999 describes a more reliable ink delivery system wherein the ink delivery tubes, thanks to a minimized flexing and breakage, provides the system with a longer expected lifetime. However, because of the tube routing , the tubes are continuously stressed to flexure. When the carriage moves back and forth along the scan axis the ink delivery tubes are stressed and also move causing fatigue. It turns into a life or maximum number of cycles that the tubes can make. When the tubes reach the end of them life, they can break due to fatigue. In addition, even if the flexing has been minimized, some infant failures can happen before their end of life.
If any of the tubes break, there is an ink leak through it. As a result, the printer may get damaged: as it is not controlled, the ink can get over the paper axis or the scan axis or even reach the electronics burning it. It is also possible that the ink gets out of the printer, reaching the user or the floor.
A possible solution to prevent the printer from getting damaged if a ink delivery tube is broken is to have a tube carrier enclosing it and completely sealed to be used as a secondary containment. So, if ink delivery tubes break, the ink gets contained between the ink delivery tube and the tube carrier, and it cannot damage the printer. However this solution still has some disadvantages. For instance, when the tubes break, there is an initial small crack that begins to grow. When the crack is big enough, the tube can kink and get completely broken, and its sharp edges can perforate the tube carrier. So, even if the tube carrier is well sealed it can be perforated by the broken tubes causing an ink leak over the scan axis. Moreover, it is more difficult to design and implement an easy-to-assemble plug system to seal the two ends of the tube carrier.
Applicant then realized that many of the above problems may be reduced by detecting the leakage when the crack has just begun.
In any case, since an ink leakage implies a major damage for the printer, an ink leak containment and detection system which detects and contains the leakage and preferably stops the printers, before a gross leak damage occurs, is desired.
The present invention provides an inkjet printing device having a frame, a transversely moveable printhead carriage, carrying at least one inkjet printhead, mounted for reciprocating movement on said frame, ink supply reservoir means mounted on said frame and flexible ink supply tubing for delivering ink from said ink reservoir means to said at least one inkjet printhead, said device further comprising an ink leakage detection system comprising:
a collecting unit, for collecting the ink leaked from the ink supply tubing; and
a sensing circuit coupled to said collecting unit, capable of detecting the presence of ink in said collecting unit.
The presence of a sensing circuit gives more benefits than a simple double containment since it can be used to warn the user to replace the tubes as soon as they break, reducing the risk of damaging the printer.
In addition the device further comprises an ink carrier, for conveying the leaked ink into the collecting unit. The ink carrier comprises additional tubing, having apertures at a first end and at a second end, coaxially containing said flexible ink supply tubing to bound so said flexible ink supply tubing, wherein the aperture at the first end of said additional tubing is sealed.
Accordingly, a manufacture may obtain an additional advantage since it is easier to design an easy-to-assemble plug system to seal just one end of the additional tubing than to seal the two ends as in a simple double containment system, and it can detect the leak in time before the tube breaks completely, reducing the risk of perforating the tube carrier.
Moreover if the tubes break, it avoids gross damage of the printer or to spread ink around, in particular on the user. This also improves the replaceability and serviceability of the ink delivery system: if the tubes break it is simpler to change the ink delivery system. In addition, this leak detection system can also work for any length of printer, and it is particularly simple and easy to implement.
The present invention further provides an inkjet printing device having a frame, a transversely moveable printhead carriage, carrying at least one inkjet printhead, mounted for reciprocating movement on said frame, ink supply reservoir means mounted on said frame and flexible tubing means for delivering ink from said ink reservoir means to said at least one inkjet printhead, said device further comprising an ink leakage detection system comprising:
collecting means, for collecting the ink leaked from the ink supply tubing; and
sensing means coupled to said collecting means, capable of detecting the presence of ink in said collecting means.
In accordance to a different aspect of the present invention there is provided a method of detecting an ink leak in an inkjet printing device comprising the step of:
a) conveying the ink leak from an ink delivery system to an ink collector;
b) sensing when ink is present in the ink collector
c) providing the information that an ink leakage is present in the device.
In accordance to a further different aspect of the present invention there is provided a method of detecting an ink leak in an inkjet printing device comprising the step of:
a) conveying the ink leak from an ink delivery system to an ink collector;
b) sensing when ink is present in the ink collector;
c) providing the information that an ink leakage is present in the device;
d) stopping the device.